Catalysts for the conversion of relatively low molecular weight hydrocarbons to higher molecular weight hydrocarbons and the regeneration of the catalysts

ABSTRACT

Novel regenerable catalyst-reagents, and a new and improved process utilizing said regenerable catalyst-reagents, for the conversion, and oligomerization of hydrocarbons, notably methane, at relatively low temperatures to produce products rich in ethylene or benzene, or both, usually in admixture with other hydrocarbons; and process for the regeneration of said catalyst-reagents. (a) The catalyst-reagents are multi-functional and are comprised of (1) a Group VIII noble metal having an atomic number of 45 or greater, nickel, or a Group I-B noble metal having an atomic number of 47 or greater; (2) a Group VI-B metal oxide which is capable of being reduced to a lower oxide, or admixture of metal oxides which includes one or more of such metal oxides; and, (3) a Group II-A metal selected from the group consisting of magnesium and strontium, composited with a suitably passivated, spinel-coated refractory support, notably an inorganic oxide support, preferably alumina; preferably calcium, composited with a suitably passivated, non-zinc containing spinel coated refractory support, notably an inorganic oxide support, preferably alumina.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of Application Ser. No. 903,814 filed May8, 1978; now U.S. Pat. No. 4,172,810.

BACKGROUND OF THE INVENTION AND PRIOR ART

It is the business of many refineries and chemical plants to obtain,process and upgrade relatively low value hydrocarbons to more valuablefeeds, or chemical raw materials. For example, methane, the simplest ofthe saturated hydrocarbons, is often available in rather largequantities either as an undesirable by product in admixture with othermore valuable higher molecular weight hydrocarbons, or as a component ofan off gas from a process unit, or units. Though methane is useful insome chemical reactions, e.g., as a reactant in the commercialproduction of methanol and formaldehyde, it is not as useful a chemicalraw material as most of the higher molecular weight hydrocarbons. Forthis reason process streams which contain methane are usually burned asfuel.

Methane is also the principal component of natural gas, which iscomposed of an admixture of normally gaseous hydrocarbons ranging C₄ andlighter and consists principally of methane admixed with ethane,propane, butane and other saturated, and some unsaturated hydrocarbons.Natural gas is produced in considerable quantities in oil and gasfields, often at remote locations and in difficult terrains, e.g.,offshore sites, arctic sites, swamps, deserts and the like. Under suchcircumstances the natural gas is often flared while the oil isrecovered, or the gas is shut in, if the field is too remote for the gasto be recovered on a commercial basis. The construction of pipelines tocarry the gas is often not economical, due particularly to the costs ofconnecting numerous well sites with a main line. Transport of naturalgas under such circumstances is also uneconomical because methane atatmospheric pressure boils at -258° F. and transportation economicsdictate that the gas be liquefiable at substantially atmosphericpressures to reduce its volume. Even though natural gas containscomponents higher boiling than methane, and such mixtures can beliquefied at somewhat higher temperatures than pure methane, thetemperatures required for condensation of the admixture is nonethelesstoo low for natural gas to be liquefied and shipped economically. Underthese circumstances the natural gas, or methane, is not even ofsufficient value for use as fuel, and it is wasted.

The thought of utilizing methane from these sources, particularlyavoiding the tremendous and absolute waste of a natural resource in thismanner, has challenged many minds; but has produced few solutions. It ishighly desirable to convert methane to hydrocarbons of higher molecularweight than methane (hereinafter, C₂ ⁺) particularly admixtures of C₂ ⁺hydrocarbon products which can be economically liquified at remotesites; especially admixtures of C₂ ⁺ hydrocarbons rich in ethylene orbenzene, or both. Ethylene and benzene are known to be particularlyvaluable chemical raw materials for use in the petroleum, petrochemical,pharmaceutical, plastics and heavy chemicals industries. Ethylene isthus useful for the production of ethyl and ethylene compounds includingethyl alcohol, ethyl ethers, ethylbenzene, styrene, ethylene oxide,ethylene dichloride, ethylene dibromide, acetic acid, polyethylene andthe like. Benzene is useful in the production of ethylbenzene, styrene,and numerous other alkyl aromatics which are suitable as chemical andpharmaceutical intermediates, or suitable in themselves as end products,e.g. as solvents or high octane gasoline components.

It has been long known that methane, and natural gas could bepyrolytically converted to C₂ ⁺ hydrocarbons. For example, methane ornatural gas passed through a porcelain tube at moderate red heat willproduce ethylene and its more condensed homologues such as propylene, aswell as small amounts of acetylene and ethane. Methane and natural gashave also been pyrolytically converted to benzene, the benzene usuallyappearing in measurable quantities at temperatures above about 1650° F.,and perhaps in quantities as high as 6-10 wt. % at 2200° F. to 2375° F.,or higher. Acetylene and benzene in admixture with other hydrocarbons,have been produced from methane and natural gas in arc processes,cracking processes, or partial combustion processes at temperaturesranging above about 2775° F. Heat for such reactions has been suppliedfrom various sources including electrically heated tubes, electricresistance elements, and spark or arc electric discharges. Theseprocesses characteristically require considerable heat energy which,most often, is obtained from combustion of the by-product gases. Theextreme temperatures make the operation of such processes uneconomicaland, of course, serious materials problems are generally encountered.Numerous attempts have been made to catalyze these reactions at lowerand more feasible temperatures, but such attempts have met with failure.

In all such processes of converting methane to C₂ ⁺ hydrocarbons apartial oxidation mechanism is involved, because hydrogen must beremoved either as water, molecular hydrogen or other hydrogen-containingspecies. Likewise, any other polymerization mechanism wherein methane isconverted to C₂ ⁺ hydrocarbon products requires a tremendous amount ofenergy, most often supplied as heat, to provide the driving force forthe reactions. In the past the molecular hydrogen liberated by thereaction has often been separated and burned to provide the necessaryprocess heat. This route has proven an abomination to the production ofC₂ ⁺ hydrocarbons, but alternate reaction pathways have appeared littlebetter, if any, for these have resulted in the production of largequantities of the higher, less useful hydrogen deficient polymericmaterials such as coke, and highly oxidized products such as carbondioxide and water.

It is nonetheless a primary objective of the present invention toobviate these and other prior art deficiencies and, in particular, toprovide the art with novel catalysts, and a catalytic process for theproduction of higher molecular weight hydrocarbons from lower molecularweight hydrocarbons, especially for the production of C₂ ⁺ hydrocarbonsfrom methane, natural gas, process streams rich in methane, and thelike.

A specific object is to provide novel regenerable catalyst-reagents, anda new and improved process utilizing said regenerable catalyst-reagents,for the conversion, and oligomerization of methane at relatively lowtemperatures to higher molecular weight hydrocarbons, particularlyproducts rich in ethylene or benzene, or both, usually in admixture withother hydrocarbons.

A yet more specific object is to provide novel regenerablecatalyst-reagents, a novel and highly economic process for the lowtemperature catalytic conversion, and oligomerization, of natural gas tomore easily liquefiable admixtures rich in C₂ ⁺ hydrocarbons, notablyethylene and benzene, which will make feasible the collection,liquefaction, shipment and use of much of the natural gas that is nowflared and wasted at remote sites.

These and other objects are achieved in accordance with the presentinvention which embodies

(a) novel multi-functional regenerable catalyst-reagents which arecomprised of (1) a Group VIII noble metal having an atomic number of 45or greater, nickel, or a Group I-B noble metal having an atomic numberof 47 or greater (Periodic Table of the Elements; Sargent WelchScientific Company, Copyright 1968), or admixture which includes one ormore of said metals; (2) a Group VI-B metal oxide of the Periodic Tableof the Elements which is capable of being reduced to a lower oxide, oradmixture of metal oxides which includes one or more of such metaloxides; and, additionally (3) a Group II-A metal selected from the groupconsisting of magnesium and strontium, or admixture which includes oneor more of such metals, composited with a suitably passivated,spinel-coated refractory support, notably an inorganic oxide support,preferably alumina; preferably calcium, composited with a suitablypassivated, nonzinc containing spinel coated refractory support, notablyan inorganic oxide support, preferably alumina;

(b) a novel hydrocarbon conversion process wherein a hydrocarbon feed,notably methane, or methane-containing gas, is contacted with acatalyst-reagent as characterized in (a), supra, at temperature rangingfrom about 1150° F. to about 1600° F., preferably from about 1250° F. toabout 1350° F., at sub-atmospheric, atmospheric, or supra atmosphericpressure sufficient to react and form C₂ ⁺ hydrocarbons; and

(c) a process for regeneration of said catalyst-reagent which has becomeinactivated as by use in the process characterized in (b), supra, bycontact thereof in an exothermic reaction with water, oxygen or anoxygen-containing gas, preferably air, at temperatures sufficient toreoxidize the Group VI-B metal oxide, or metal oxides, and preferablyalso sufficient to provide the required sensible heat to said novelhydrocarbon conversion process (b), supra, on recycle of thecatalyst-reagent; which suitably ranges from about 1000° F. to about1600° F., preferably from about 1250° F. to about 1450° F., carbondioxide and water being released in the regeneration reaction.

The novel catalyst-reagents are multi-functional and, though the exactnature of the reaction paths are by no means certain, the includedcomponents are believed to play different mechanistic functions in theproduction of oligomers from the low molecular weight hydrocarbon feeds,notably methane. The Group I-B (silver, gold) or VIII (rhodium,palladium, osmium, iridium and platinum) noble metal, or nickel, thefirst essential component, of which the Group VIII noble metals, notablyplatinum, iridium and palladium, but particularly platinum, arepreferred, is believed to enter into a dissociative chemisorptionreaction with the hydrocarbon feed and cause it to lose hydrogen. Forexample, in the reaction with methane, the Group I-B or Group VIII noblemetal, or nickel, functions to cause dissociative chemisorption of themethane onto the surface of the catalyst to produce species which canreact to form ethylene directly, another species which reacts to formethane and higher molecular weight aliphatic hydrocarbons, or both, andother species which can directly react with the Group VI-B metal oxideto form water.

The Group VI-B metal oxide, the second essential component, ischaracterized as an oxide which is capable of being reduced in thereaction to a lower oxide or the zero valent metal, or both. Thereducible Group VI-B metal oxide component, comprising an oxide, oroxides, of the multivalent metals chromium, molybdenum and tungsten, isbelieved to provide a catalytic function, in addition to the reagentfunction which is a function of the change of oxidation state of themetal. Thus, it acts as a reagent in that it is believed to donateoxygen for reaction with abstracted hydrogen to form water and therebyprovide the energy necessary to sustain the reaction. In its catalyticfunction, it is believed that the low valence oxides of the Group VI-Bmetal, or the completely reduced metal, provide a cyclization functionwhereby acetylene, acetylides and the like, and perhaps even ethyleneare converted into aromatics, notably benzene. Thus, it is one or moreof the products of the reagent function of the Group VI-B metal oxidecomponents which are believed to provide the catalytic function of theGroup VI-B metals.

It has also been found that the activity of the Group VI-B reducablemetal oxide to react with abstracted hydrogen and form water can besupplemented, or enhanced, by the additional presence of oxides of (i)Group III-A metals having an atomic number of 31 or greater (gallium,indium and thallium), (ii) Group IV-B transition metals of atomic numberranging from 22 to 40 (titanium and zirconium), (iii) Group V-Btransition metals (vanadium, niobium and tantalum), (iv) Group VII-Btransition metals (manganese and rhenium), (v) Group VIII nonnoblemetals of atomic number ranging from 26 to 27 (iron and cobalt), (vi)metals of the lanthanum series of atomic number ranging from 58 to 71(cerium, praseodymium, neodynium, samarium, europium, gadolinium,terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium), and(vii) metals of the actinum series of atomic number ranging from 90 to92 (thorium and uranium). Of these, the preferred oxygen donor compoundscomprise the oxides of vanadium, niobium, rhenium, cerium and uranium.

The Group II-A, or alkaline-earth metals (magnesium, strontium, andcalcium), of which calcium is preferred, constitute the third essentialcomponent of the catalyst. The Group II-A metal is put on the catalystsupport as an oxide and, in performing its function, is believed to forma Group II-A metal carbide, or carbides as intermediates during thecourse of the reaction. This, of course, does not suggest that otherspecies containing the Group II-A metal are not formed, and possiblyactive during the reaction. However, in an initial stage it is believedthat the oxide of the Group II-A metal supplies oxygen which reacts withabstracted hydrogen to form water, thus providing some of the energy forthe reaction. Calcium is believed to function particularly well in thisaspect. The Group II-A metal carbides, particularly carbides of theheavier Group II-A metals, are also believed to form compounds whichpossess carbon-carbon bonds, or polycarbon-carbides, particularly C₂species or acetylides, which are thought to be intermediates, orprecursors of intermediates, in the formation of cyclic compounds.

It is also essential in formation of these catalysts that the severalcomponents be composited with a passivated surface, spinel-coatedinorganic metal oxide support, preferably a spinel-coated alumina uponwhich the several components are sequentially impregnated, orcoimpregnated by any of the common techniques in use for the preparationof heterogeneous catalysts. The term "spinel," as used herein,designates a binary oxide which is characterized as having either anormal or inverse spinel structure. The normal spinel structure can berepresented by the formula MY₂ O₄ wherein M and Y are cations ofdifferent metals, and the inverse spinel structure can be represented bythe formula Y(XY)O₄ wherein Y and X are cations of different metals. Thesum of the cationic charges of a spinel, whether normal or inverse, isequal to 8. A description of the spinel-type structures is found inStructural Inorganic Chemistry, A. F. Wells, 3rd Edition, Oxford, theClarendon Press, 1962, at pages 487-488, herewith incorporated byreference.

While calcium is the preferred Group II-A reagent metal it isnonetheless essential that calcium reagent not be employed in thepresence of zinc. This is true even when the zinc is present as aconstituent or part of the passivated, spinel-coated surface, e.g., aswhen the calcium is deposited on a zinc aluminate spinel carrier, orzinc aluminate spinel coated support. The presence of zinc, among otherthings, causes the formation of considerable amounts of coke withdrastic reduction in the formation of the desired products.

Thermodynamic considerations of the possible reaction paths leave littledoubt but that numerous possible reaction paths favor the formation of aconsiderable amount of coke and/or carbon dioxide, with little or noyield of potentially valuable products, a conclusion which fits wellwith the results of many past experiments. However, pursuant to thepractice of this invention, albeit some coke, polymeric, or carbonaceousmaterial is produced, essentially all of this material that is formed inthe reaction is burned to carbon dioxide and fully utilized in theregeneration stage to provide process heat. On the other side of theprocess, relatively little carbon dioxide is formed in the reactionstaking place in the main reactor. It has been demonstrated that thecatalyst-reagents of this invention, under the desired conditions forconducting the process, produce products containing an admixture ofvaluable oligomers, particularly ethylene and benzene.

Though the exact nature of the reaction paths is by no means certain, assuggested, it is believed that the Group I-B noble metals and Group VIIInoble metals, inclusive of nickel, function to cause one or moredissociative chemisorptions of the methane onto the surface of thecatalyst to produce species which may react to form ethylene directly,or another species which may react to form ethane and higher molecularweight aliphatic hydrocarbons, or both, and another species such asadsorbed hydrogen, which may react directly with the transition metal orother oxide to form water. Or such species may react with the Group II-Acarbides to liberate ethylene, form acetylene, or other products, formintermediates which lead to cyclization, or react with cyclization orpolymerization products to form benzene or other products which appearin the exit gases from the reactor. The Group VI-B metal oxide also mayreact directly with abstracted or liberated hydrogen to form water, andby interaction with a Group I-B noble metal or Group VIII noble metal,or nickel, is believed to form water and a species which further reactsto form ethylene. Where methane is used as a feed, it is thus envisionedthat the reaction mechanisms with a multivalent Group I-B noble metal orGroup VIII noble metal, or nickel, referred to as "M", may include thefollowing sequences of reactions, to wit: ##STR1##

    (2) 2MCH.sub.3 →2M°+H.sub.3 C--CH.sub.3 (2)

    (3) MCH.sub.3 +M°→M═CH.sub.2 +MH (3)

    (4) 2M═CH.sub.2 →2M°+H.sub.2 C═CH.sub.2 (4)

and, ##STR2## It is also envisioned that the multivalent transitionmetal oxide, M'O_(n), the transition metal being designated as M', theoxygen as O, with the subscript n representing the number of oxygenatoms associated with M', or the ratio of oxygen atoms to M atoms in theassociation since n need not be an integer, reacts with the intermediateMH [Equation (1), supra] as follows:

    (6) 2MH+M'O.sub.n →M°+M'O.sub.n-1 +H.sub.2 O (6)

and with abstracted and liberated hydrogen as follows;

    M'O.sub.n +H.sub.2 →M'O.sub.n-1 +H.sub.2 O          (7)

and, M' participates with M in reacting with methane, as follows:

    (8) M'O.sub.n +CH.sub.4 +M°→M'O.sub.n-1 +H.sub.2 O+M═CH.sub.2                                          ( 8)

Likewise, MO_(n-1) and M'O_(n-1) can further react in similar manner toproduce additional water, ethylene, ethane, and other hydrocarbons untilthe valence of M, M' and M" have been reduced to some lower level or tozero, at which time further reactions such as described are no longerpossible without reoxidation of the catalyst by regeneration.

The presence of the Group II-A metal, or alkaline earth metal component,favors the production of larger amounts of benzene in the products ofthe reaction. In this type of reaction, it is believed that the methaneor organometallic intermediates interact with the Group II-A metalcomponent to form metal carbides and water. The carbides, acetylides,propadiynides and the like, it is believed, react in turn with the wateror abstracted or liberated hydrogen to generate benzene, ethylene,and/or the other products of the process.

It is known that acetylene can be trimerized at certain conditions toyield benzene, but it is also known that free acetylene also has apropensity to react to form coke; which form of reaction is highlyundesirable. Such reaction can thus be represented by the followingequation, to wit:

    C.sub.2 H.sub.2 →Heat+(C.sub.2).sub.x +H.sub.2 (or Coke+H.sub.2) (9)

In the catalytic reaction of this invention, however, it is not believedthat free acetylene is formed and whereinafter C₂ H₂ is represented inthe equation, the acetylene is believed present only as a transient, ormolecular species complexed with one or more metal atoms, and which israpidly converted into benzene, ethylene or other hydrocarbon or coke.Therefore, it is theorized that the reaction pathway to the formation ofbenzene may be shown by equations 10-16, infra. Representing a GroupII-A metal as M", and a carbide, acetylide, or the like of such metalsas M"_(m) C, M"_(m) C₂, M"_(m) C₃, the designations denoting the degreeof association of carbon/carbide atoms within the material, all of whichgenerally fit in the "metal carbide" category, and the subscriptsdenoting generally the number of metal atoms associated with eachcarbide anion carbon or group of carbons, the following reactions arebelieved to occur in forming the carbides, acetylides, to wit:

    2M"O+CH.sub.4 →M".sub.2 C+2H.sub.2 O (10)

    M".sub.2 C, M"C, etc.→M"C.sub.2, M"C.sub.3, M".sub.2 C.sub.3, etc. (11)

The acetylene forming reaction is representing by the followingequation, to wit:

    M"C.sub.2 +H.sub.2 O→M"O+C.sub.2 H.sub.2            ( 12)

The acetylene trimerization may be represented by the followingequation:

    3C.sub.2 H.sub.2 +Catalyst→C.sub.6 H.sub.6 +Catalyst (13)

Where the catalyst is M'° or lower valent M'O_(z) and a similar sort ofdimerization of C₃ materials is likewise possible. An alternate morelikely cyclization route can also take place, directly from the carbide,to wit:

    3M"C.sub.2 +M'O.sub.2 →2M"O+M'C.sub.6, etc.         (14)

    M'C.sub.6 +6MH→6M°+M'°+C.sub.6 H.sub.6 ( 15)

    2M"C.sub.3 +M'O.sub.2 →2M"O+M'C.sub.6               ( 16)

    M'C.sub.6 +6CH.sub.4 +6M°→M'+6MCH.sub.3 +C.sub.6 H.sub.6 ( 17)

Another alternate pathway for the cyclization to benzene involves thedehydrogenation and cyclization of three ethylenes via reactions on theM and M' catalyst and reagent metals.

However, it is also possible that the reaction pathway to C₂ ⁺hydrocarbons, inclusive of ethylene and benzene may be through thecatalytic or thermal formation of a particular type of "coke" whichcatalytically or thermally decomposes in the reaction to form thethermally stable volatile products, benzene and ethylene, to wit:

    CH.sub.4 +Catalyst→"Coke"+Catalyst+H.sub.2 O        (18)

    "Coke"+Catalyst (+2CH.sub.4)→Coke+C.sub.2 H.sub.4 +C.sub.6 H.sub.6 ( 19)

The catalyst or feed, or both, may be furnishing hydrogen to decomposethe "Coke" as, to wit:

    M°+CH.sub.4 →MH+"Coke"                       (20)

    MH+"Coke"→M°+C.sub.2 H.sub.4 +C.sub.6 H.sub.6 ( 21)

In the preparation of the catalyst-reagents, a porous metal oxidesupport, preferably one which has been desurfaced by contact with steam,is first passivated and the surface thereof converted to a spinel. Thisis accomplished by treatment of the support with at least one metalcomponent (other than zinc when calcium is to be deposited on thesupport), preferably a metal from Group II-A, such that the sum of theionic charges of the metal of the metal oxide support and the metallicelement, or metallic elements, of the metal component used to treat thesupport satisfy the requirement for spinel formation, i.e., that the sumof the valences equals 8 and the ionic radii of the metals satisfy therequirements for formation of the normal or inverse spinel typestructures. Exemplary of materials which can be used as supports aremagnesium oxide, titanium oxide, zirconium oxide, hafnium oxide, and thelike, preferably alumina. Suitably, the metal oxide support, preferablyone having an initial surface area ranging from about 50 m² /g to about250 m² /g, preferably above 150 m² /g, is treated by contact, andimpregnation with a solution of a compound of the desired metalcomponent which is deposited on the metal oxide support. The treated orimpregnated metal oxide is subsequently calcined, suitably at atemperature ranging from about 925° F. to about 1825° F., this producinga surface spinel or spinel-coating on the metal oxide support. Thespinel surfaced support is then treated with a solution, or solutions,containing compounds which provide the essential substituentscharacterized in (a), supra.

The several components are deposited on the passivated, spinel-coatedsupport by the impregnation method. Pursuant to this method, a compound,or compounds which contain the desired metal, or metals, are dissolvedin solution in the desired concentration. The support in solvated, dryor calcined state is contacted with the metal or metals-containingsolution, or solutions, and thereby impregnated by either the so-called"incipient wetness" technique, or technique embodying absorption from adilute solution, or solutions, with subsequent drying of the support. Inthe impregnation procedure, the Group II-A metal is generally firstimpregnated onto the passivated, spinel-coated support; the amount addedto the support being additional to any such similar or dissimilar metalwhich may have been used to form the spinel-coating, since that used informing the spinel is not contained thereon in active form. The GroupII-A metal impregnated support is then, preferably, calcined in an inertor oxidizing atmosphere and the Group VI-B metal is then impregnatedonto the support, and again calcined. Suitably also, compounds of theGroup II-A and VI-B metals can be coimpregnated onto the passivated,spinel-coated surface and the support then dried and calcined. It isessential, in either event, after deposition of the Group VI-B metal tocalcine the catalyst-reagent in an oxidizing atmosphere, i.e., in thepresence of air or an oxygen-containing gas, to convert the Group VI-Bmetal to an oxide. The Group III-A, and transition metals of IV-B, V-B,VII-B, inclusive also of the lanthanide and actinium series metals, andiron and cobalt, alone or in admixture with other metals are similarlyimpregnated onto the support and the impregnated support calcined in anoxidizing atmosphere to form an oxide, or oxides of the metal. The GroupI-B or Group VIII noble metal, or nickel, is generally impregnated ontothe passivated, spinel-coated support after deposition of the otheressential components and then calcined, suitably in air; or added bycoimpregnation with one or more of the other essential or non-essentialcomponents. Where the impregnating compound contains halogen, or otherundesirable component, wet calcination may be employed to remove thehalide from the catalyst-reagent. In all embodiments, the support can betreated by contact with a single solution containing the desired amountsof a metal, or metals, or treated sequentially by contact with asolution containing one metal, and then with a solution which containsanother metal, or metals, in the desired amounts. Large particles,whether pilled, pelleted, beaded or extruded, can be so-treated and thencrushed to the desired size, or the particle can be pre-reduced in size,and then treated. The catalyst-reagent, in either instance, can then bedried, calcined and then contacted as fixed, fluidized or moving bedwith the feed at the desired reaction conditions.

In the preparation of the catalyst-reagents the Group I-B or Group VIIInoble metals, or nickel, is deposited on the support in concentrationranging from about 0.01 percent to about 2 percent, preferably fromabout 0.1 to about 1 percent, calculated as metallic metal based on theweight of the total catalyst-reagent (dry basis). The reducable GroupVI-B metal oxide is deposited on the catalyst-reagent in concentrationsufficient to supply at least one-half of an atom of oxygen for eachhydrocarbon molecule which is to be oligomerized, and preferably atleast one atom of oxygen for each hydrocarbon which is to beoligomerized. Generally, at least about 1.1:1 to at least 1.5:1 atoms ofoxygen are supplied for each molecule of methane when high ethylenecontent is desired in the product. At least 1.5:1 atoms of oxygen aresupplied for each molecule of methane when high benzene content isdesired in the product. The Group VI-B metal is deposited on thecatalyst-reagent in concentration ranging from about 1 percent to about20 percent, preferably from about 3 percent to about 10 percent,calculated as metallic metal based on the weight of the totalcatalyst-reagent (dry basis). Suitably also the oxides of the GroupIII-A metals, the oxides of the Group IV-B, V-B, VII-B transitionalmetals, the oxides of iron, cobalt and the oxides of the metals of thelanthanide and actinide series are deposited on the catalyst inconcentration ranging from about 0.01 percent to about 25 percent,preferably from about 5 percent to about 15 percent calculated asmetallic metal based on the weight of the total catalyst-reagent (drybasis). The oxide of the Group II-A, or alkaline earth metal isdeposited on the catalyst-reagent in concentration ranging from about 1percent to about 30 percent, preferably from about 5 percent to about 25percent calculated as metallic metal based on the weight of the totalcatalyst-reagent (dry basis). In compositing these metals with thecatalyst-reagent, the Group II-A metal is composited in an amountsufficient to provide an atomic ratio of at least about 3:1 relative tothe Group VI-B metal, and preferably the ratio of the Group IImetal/Group VI-B metal ranges from about 3:1 to about 40:1, preferablyfrom about 5:1 to about 12:1 when a relatively high concentration ofbenzene is desired in the product.

The catalyst-reagent, particularly in view of its dual role as reagentand catalyst, eventually loses its activity and its activity must berestored. Restoration of the activity of the catalyst-reagent isperformed by oxidative regeneration, i.e., by contact of thecatalyst-reagent with water, oxygen or oxygen-containing gas, preferablyair, at temperatures sufficiently elevated to burn off accumulated cokeand reoxidize the Group VI-B metals and Group II-A metals; as well asthe metals of Groups III-A, IV-B, V-B, VII-B, iron, cobalt and thelanthanides and actinides, to the extent they are present in thecatalyst-reagent. Temperatures on the order of about 700° F. aregenerally adequate to reoxidize these metals and restore the activity ofthe catalyst-reagent, but preferably temperatures on the order of about1000° F. to about 1600° F., more preferably from about 1250° F. to about1450° F., are employed in the regeneration zone and the hot regeneratedcatalyst-reagent is recycled to the hydrocarbon reaction zone inquantity sufficient to supply the sensible heat needed for the reaction.Generally, adequate heat is maintained by burning the coke from thecatalyst-reagent during the regeneration. Pressure, while not critical,is generally maintained above atmospheric, suitably between atmosphericand about 20 atmospheres.

The invention will be more fully understood by reference to thefollowing non-limiting examples which illustrate its more salientfeatures. All parts are in terms of weight except as otherwisespecified.

EXAMPLES

Catalyst-reagents were prepared from spinel blocked alumina supportsmade by impregnating via the incipient wetness technique a commerciallyavailable, high purity gamma alumina calcined at 1000° F. for two hoursto produce an alumina having a surface area of 193 m² /g (B.E.T.) withan aqueous solution of a salt of the blocking metal. For example, in thepreparation of a CaAl₂ O₄ spinel blocked alumina support, as forcatalyst-reagent F, a calcium nitrate solution was formed by dissolvingmagnesium nitrate in water, and the calcium solution was then added tothe support in amount calculated to deposit 3.5 percent Ca onto thesupport. The impregnated support was dried, and then subjected to asubsequent calcination at 1000° F. for four hours, and at 1300° F. foran additional hour. The CaAl₂ O₄ spinel blocked alumina support was thenimpregnated with an aqueous solution of a salt of the desired Group II-Ametal, e.g., calcium nitrate, as in the preparation of Catalyst F, andcalcined for 4 hours at 1000° F. Impregnation was also via the incipientwetness technique with subsequent calcination, alternate impregnationsand calcinations having been conducted a number of times in sequence tobring the Group II-A metal concentration to the desired concentration.After the final calcination, a Group VI-B metal, Cr was deposited from asolution of a salt of the Group VI-B metal onto the catalyst-reagent toprovide the desired Group VI-B metal concentration after calcination for4 hours at 1000° F. with subsequent calcination in air at 1300° F. for 1hour. The calcined catalyst-reagent was then impregnated by adsorptionfrom dilute solution with an acid salt of the Group VIII noble metal,e.g., a hexachloroplatinic acid, H₂ PtCl₄, solution sufficient toprovide the desired concentration of platinum on the catalyst-reagent,and again calcined for 16 hours in air at 1300° F.

A 5 gram portion of each catalyst was charged into a quartz tube furnaceand heated slowly at essentially ambient pressure with a flowing streamof nitrogen over a period of 6 hrs. to 1300° F. The flow of nitrogen wasthen discontinued, and then a stream of essentially pure methane (99.4%)was passed across the catalyst-reagent for 30 minutes. The flow ofmethane was then discontinued and nitrogen was again introduced, thenitrogen having been substituted at the end of this period to act as acarrier gas. The entire effluent was collected in a neoprene rubber bagduring the time that hydrocarbons were evolved from the system. A sampleof the collected product was then subjected to a mass spectrometric gasanalysis to determine the hydrocarbon components present in the gaseousproduct in significant quantity, and the amount of coke deposited on thecatalyst was measured.

The results obtained are given in Table I below:

                                      TABLE I                                     __________________________________________________________________________    TESTING OF CATALYST REAGENTS FOR METHANE POLYMERIZATION                       Test Run Number                                                                              7     8     9       10                                         __________________________________________________________________________    Catalyst Designation                                                                         E     F     F.sub.2 G                                          Nominal Catalyst Type                                                                        CaCrPt                                                                              CaCrPt                                                                              CaCrPt  CaMoVPt                                    Use            Original.sup.(1)                                                                    Original.sup.(1)                                                                    Regenerated.sup.(2)                                                                   Original.sup.(1)                           Base Material M'"" .sub.m O.sub.n                                                            γ-Al.sub.2 O.sub.3                                                            γ-Al.sub.2 O.sub.3                                                            γ-Al.sub.2 O.sub.3                                                              γ-Al.sub.2 O.sub.3                   Blocking Metal M""                                                                           Zn    Ca.sup.(3)                                                                          Ca.sup.(3)                                                                            Ca.sup.(3)                                 Concentration Blocking Metal                                                                 5.7   3.5   3.5     3.4                                        M"" (Wt. %)                                                                   Metal M        Pt    Pt    Pt      Pt                                         Concentration M (Wt. %)                                                                      0.2   0.2   0.2     0.3                                        Metal M'       Cr    Cr    Cr      Mo                                         Concentration M' (Wt. %)                                                                     3.8   3.8   3.8     7.0                                        Metal M"       Ca    Ca    Ca      Ca                                         Concentration M" (Wt. %)                                                                     8.3   8.3   8.3     9.2                                        Metal M'"      --    --    --      V                                          Concentration M'" (Wt. %)                                                                    0.0   0.0   0.0     10.2                                       Product Analysis                                                              Component (Mole %)                                                            CH.sub.4       63.24 39.93 46.20   44.75                                      C.sub.2 H.sub.2                                                                              --    --    --      0.03                                       C.sub.2 H.sub.4                                                                              0.03  2.33  2.87    3.64                                       C.sub.2 H.sub.6                                                                              0.16  0.38  0.46    0.19                                       C.sub.3 H.sub.6                                                                              --    --    --      0.02                                       C.sub.3 H.sub.8                                                                              --    0.01  --      0.00                                       C.sub.4 H.sub.8                                                                              0.005 --    0.01    0.00                                       n-C.sub.4 H.sub.10                                                                           0.01  --    0.02    0.01                                       C.sub.6 H.sub.6                                                                              0.00  2.14  2.46    1.99                                       N.sub.2        36.55 55.21 47.98   49.37                                      Product Composition                                                           Component (Wt. %)                                                             CH.sub.4       49.61 26.34 31.23   30.34                                      C.sub.2 H.sub.2                                                                              --    --    --      0.03                                       C.sub.2 H.sub.4                                                                              0.04  2.69  3.39    4.32                                       C.sub.2 H.sub.6                                                                              0.24  0.47  0.58    0.24                                       C.sub.3 H.sub.6                                                                              --    --    --      0.04                                       C.sub.3 H.sub.8                                                                              --    0.02  --      0.00                                       C.sub.4 H.sub.8                                                                              0.01  --    0.02    0.01                                       n-C.sub.4 H.sub.10                                                                           0.03  --    0.05    0.02                                       C.sub.6 H.sub.6                                                                              0.00  6.87  8.10    6.57                                       N.sub.2        50.07 63.60 56.63   58.44                                      Coke on Catalyst (Wt. %).sup.(4)                                                             28.73 2.48  2.16    1.74                                       Coke on Catalyst After                                                         Regeneration (Wt. %).sup.(6)                                                                0.24  0.11  0.22    0.16                                       __________________________________________________________________________     .sup.(1) Original catalysts used in first cycle of methane polymerization     .sup.(2) F.sub.2  Catalyst F once regenerated, used in the second cycle o     methane polymerization.                                                       .sup.(3) Concentration of blocking reagent metal M"" used for spinel          formation is not included as part of M" concentration even though the         identical metal was used for both purposes.                                   .sup.(4) "Coke on Catalyst" may also include significant quantities of        metal carbide "carbon.                                                        .sup.(5) Testing at 1 atm. pressure, pure CH.sub.4 feed, N.sub.2 purge        before and after, 0.5 hrs/run except first cycle on B above at 4.0 hrs.       .sup.(6) Regeneration by final 700° C. air burning.               

From these data it will be observed that catalysts which contain theGroup II-A metal catalyst component, except where zinc is present (TestRun Number 7), are quite effective in oligomerizing methane to produceproduct compositions rich in ethylene and benzene. Where zinc ispresent, however, a major amount of the methane is converted to coke,with minimal production of C₂ ⁺ gases.

It is apparent that various modifications and changes can be madewithout departing the spirit and scope of the invention.

What is claimed is:
 1. A multi-functional regenerable catalyst-reagentcomposition suitable for the oligomerization of hydrocarbons whichcomprises (1) a Group VIII noble metal having an atomic number of 45 orgreater, nickel, or a Group I-B noble metal having an atomic number of47 or greater, (2) a Group VI-B metal oxide which is capable of beingreduced to a lower oxide, and (3) a Group II-A metal selected from thegroup consisting of magnesium and strontium, composited with aspinel-coated refractory support, or calcium composited with a non-zinccontaining spinel-coated refractory support.
 2. The composition of claim1 wherein the Group VIII noble metal is platinum, iridium or palladium.3. The composition of claim 1 wherein the Group VI-B metal is chromium,molybdenum or tungsten.
 4. The composition of claim 1 wherein the GroupII-A metal is calcium.
 5. The composition of claim 1 wherein thespinel-coated inorganic oxide is alumina.
 6. The composition of claim 1wherein the Group VIII noble metal is platinum, the Group VI-B metal ischromium, molybdenum or tungsten, and the Group II-A metal is calcium.7. The composition of claim 1 wherein the Group VIII noble metal isplatinum, the Group VI-B metal is chromium, molybdenum or tungsten, theGroup II-A metal is calcium, and the support is alumina.
 8. Thecomposition of claim 1 wherein the catalyst-reagent composition containsadditionally a Group III-A metal having an atomic number of 31 orgreater, a IV-B, V-B or VII-B transition metal, iron, cobalt, or a metalof the actinide or lanthanide series.
 9. The composition of claim 1wherein the Group VIII noble metal is platinum, the Group VI-B metal ischromium, molybdenum or tungsten, the Group II-A metal is calcium, thesupport is alumina, and the catalyst-reagent composition containsadditionally a Group III-A metal having an atomic number of 31 orgreater, a IV-B, V-B or VII-B transition metal, iron, cobalt, or a metalof the actinide or lanthanide series.
 10. A process for the regenerationof a catalyst-reagent which has become inactivated in a hydrocarbonconversion reaction which comprisescontacting said catalyst-reagentcomprising (1) a Group VIII noble metal having an atomic number of 45 orgreater, nickel, or a Group I-B noble metal having an atomic number of47 or greater, (2) a Group VI-B metal oxide which is capable of beingreduced to a lower oxide, and (3) a Group II-A metal selected from thegroup consisting of magnesium and strontium, composited with aspinel-coated refractory support, or calcium composited with a non-zinccontaining spinel-coated refractory support with water, oxygen or anoxygen-containing gas at temperatures ranging from about 1000° F. toabout 1600° F.
 11. The process of claim 10 wherein the Group VIII noblemetal is platinum, iridium or palladium.
 12. The process of claim 10wherein the Group VI-B metal is chromium, molybdenum or tungsten. 13.The process of claim 10 wherein the Group II-A metal is calcium.
 14. Theprocess of claim 10 wherein the spinel-coated inorganic oxide isalumina.
 15. The process of claim 10 wherein the Group VIII noble metalis platinum, the Group VI-B metal is chromium, molybdenum or tungsten,and the Group II-A metal is calcium.
 16. The process of claim 10 whereinthe Group VIII noble metal is platinum, the Group VI-B metal ischromium, molybdenum or tungsten, the Group II-A metal is calcium, andthe support is alumina.
 17. The process of claim 10 wherein thecatalyst-reagent composition contains additionally a Group III-A metalhaving an atomic number of 31 or greater, a IV-B, V-B or VII-Btransition metal, iron, cobalt, or a metal of the actinide or lanthanideseries.
 18. The process of claim 10 wherein the Group VIII noble metalis platinum, the Group VI-B metal is chromium, molybdenum or tungstenthe Group II-A metal is calcium, the support is alumina, and thecatalyst-reagent composition contains additionally a Group III-A metalhaving an atomic number of 31 or greater, a IV-B, V-B or VII-Btransition metal, iron, cobalt, or a metal of the actinide or lanthanideseries.
 19. The process of claim 10 wherein the catalyst-reagentcontains coke deposits, and coke is burned from the catalyst to generateprocess heat.
 20. The composition of claim 1 wherein the Group VIIInoble metal, nickel or Group I-B noble metal is deposited on the supportin concentration ranging from about 0.01 percent to about 2 percent,calculated as metallic metal based on the weight of the totalcatalyst-reagent.
 21. The composition of claim 20 wherein the Group VIIInoble metal, nickel or Group I-B noble metal is deposited on the supportin concentration ranging from about 0.1 percent to about 1 percent. 22.The composition of claim 1 wherein the Group VI-B metal oxide isdeposited on the catalyst-reagent in concentration ranging from about 1percent to about 20 percent calculated as metallic metal based on theweight of the total catalyst-reagent.
 23. The composition of claim 1wherein the Group VI-B metal oxide is deposited on the catalyst-reagentin concentration ranging from about 3 percent to about 10 percent. 24.The composition of claim 1 wherein the Group II-A metal is deposited onthe catalyst-reagent in concentration ranging from about 1 percent toabout 30 percent calculated as metallic metal based on the weight of thetotal catalyst-reagent.
 25. The composition of claim 24 wherein theGroup II-A metal is deposited on the catalyst-reagent in concentrationranging from about 5 percent to about 25 percent.
 26. The composition ofclaim 22 wherein the Group II-A metal is provided in atomic ratio of atleast about 3:1 relative to the Group VI-B metal.
 27. The composition ofclaim 26 wherein the Group II-A metal is provided in atomic ratio of atleast about 3:1 to about 40:1.
 28. The composition of claim 27 whereinthe Group II-A metal is provided in atomic ratio of at least about 5:1to about 12:1.
 29. The composition of claim 1 wherein the Group VIIInoble metal is platinum, the Group VI-B metal is chromium, molybdenum ortungsten, the Group II-A metal is magnesium, strontium or calcium, andthe support is magnesium oxide, titanium oxide, zirconium oxide orhafnium oxide.
 30. The process of claim 10 wherein the Group VIII noblemetal, nickel or Group I-B noble metal is deposited on the support inconcentration ranging from about 0.01 percent to about 2 percent,calculated as metallic metal based on the weight of the totalcatalyst-reagent.
 31. The process of claim 30 wherein the Group VIIInoble metal, nickel or Group I-B noble metal is deposited on the supportin concentration ranging from about 0.1 percent to about 1 percent. 32.The process of claim 10 wherein the Group VI-B metal oxide is depositedon the catalyst-reagent in concentration ranging from about 1 percent toabout 20 percent calculated as metallic metal based on the weight of thetotal catalyst-reagent.
 33. The process of claim 30 wherein the GroupVI-B metal oxide is deposited on the catalyst-reagent in concentrationranging from about 3 percent to about 10 percent.
 34. The process ofclaim 10 wherein the magnesium, strontium or calcium is deposited on thecatalyst-reagent in concentration ranging from about 1 percent to about30 percent calculated as metallic metal based on the weight of the totalcatalyst-reagent.
 35. The process of claim 34 wherein the magnesium,strontium or calcium is deposited on the catalyst-reagent inconcentration ranging from about 5 percent to about 25 percent.
 36. Theprocess of claim 32 wherein the magnesium, strontium or calcium isprovided in atomic ratio of at least about 3:1 relative to the GroupVI-B metal.
 37. The process of claim 36 wherein the magnesium, strontiumor calcium is provided in atomic ratio of at least about 3:1 to about40:1.
 38. The process of claim 37 wherein the magnesium, strontium ofcalcium is provided in atomic ratio of at least 5:1 to about 12:1. 39.The process of claim 10 wherein the Group VIII noble metal is platinum,the Group VI-B metal is chromium, molybdenum or tungsten, the Group II-Ametal is magnesium, strontium or calcium, and the support is magnesiumoxide, titanium oxide, zirconium oxide or hafnium oxide.